What is the name of the doctrine that President James Polk belived in that stated that it was the god given right for the US to expand and claim lands from coast to coast?

The doctrine that President James Polk believed in is known as "Manifest Destiny." This belief held that it was America's divine right and destiny to expand its territory across the North American continent, from the Atlantic to the Pacific Ocean. It justified the westward expansion and was a significant factor in U.S. policies during the 19th century, including the annexation of Texas and the Oregon Territory.